Climatic Clues from Restricted Seas
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Fig. 7.13. Bathymetric distribution of the abundant benthic foraminifera in the western Baltic. Width
of black columns indicates number of living specimens found per IO cm 2 seaboltom (Ammoscalaria:
only empty shells were found in I 963/64). The wavy line at about 14 m depth marks the boundary
between outtlowing surface water and incoming marine water. [G. F. Lutze, 1965 , Meyniana 15: 75]
velops a serious oxygen deficiency, with values of less than 10% saturation. Under
certain condition all the oxygen can be used up, and H2S (the foul-smelling gas)
develops from bacterial sulfate reduction.
7.6.3 Condition of Stagnation. As the oxygen content drops, the bottom fauna
changes. At a concentration of less than I ml 02 per liter of water, shelled organisms
disappear. Only a few species of metazoans remain: mainly worms (annelids, nematodes) and crustaceans. They stir the uppermost sediment, feeding on deposits, leaving burrows but essentially no hard parts. Below 0.1 ml 02 per liter the environment
becomes hostile to all metazoans; only some protists survive, and the various anaerobic bacteria.
As mentioned, both high productivity and stable stmtification are responsible for
the oxygen deficiency in Baltic bottom waters. If nutrient supply is then involved in
producing oxygen deficiency, could man 's activities increase "stagnation" of the
Baltic? Certainly. Deforestation and agriculture greatly increase soil erosion and
hence the input of soil extracts, that is, nutrients. Also, modem agricultural methods
in surrounding regions rely on fertilizer, much of which enters the Baltic Sea with the
runoff. Sewage and industrial waste is yet another source. Thus, stagnation is indeed
favored by man's activities. However, sediment cores from the centml Baltic show
that stagnation occurred frequently even before human factors could playa role. This
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Fig. 7.13. Bathymetric distribution of the abundant benthic foraminifera in the western Baltic. Width
of black columns indicates number of living specimens found per IO cm 2 seaboltom (Ammoscalaria:
only empty shells were found in I 963/64). The wavy line at about 14 m depth marks the boundary
between outtlowing surface water and incoming marine water. [G. F. Lutze, 1965 , Meyniana 15: 75]
velops a serious oxygen deficiency, with values of less than 10% saturation. Under
certain condition all the oxygen can be used up, and H2S (the foul-smelling gas)
develops from bacterial sulfate reduction.
7.6.3 Condition of Stagnation. As the oxygen content drops, the bottom fauna
changes. At a concentration of less than I ml 02 per liter of water, shelled organisms
disappear. Only a few species of metazoans remain: mainly worms (annelids, nematodes) and crustaceans. They stir the uppermost sediment, feeding on deposits, leaving burrows but essentially no hard parts. Below 0.1 ml 02 per liter the environment
becomes hostile to all metazoans; only some protists survive, and the various anaerobic bacteria.
As mentioned, both high productivity and stable stmtification are responsible for
the oxygen deficiency in Baltic bottom waters. If nutrient supply is then involved in
producing oxygen deficiency, could man 's activities increase "stagnation" of the
Baltic? Certainly. Deforestation and agriculture greatly increase soil erosion and
hence the input of soil extracts, that is, nutrients. Also, modem agricultural methods
in surrounding regions rely on fertilizer, much of which enters the Baltic Sea with the
runoff. Sewage and industrial waste is yet another source. Thus, stagnation is indeed
favored by man's activities. However, sediment cores from the centml Baltic show
that stagnation occurred frequently even before human factors could playa role. This